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Taxonomy is the branch of biology that deals with the identification and naming of living organisms

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Introduction

Mr. Miller Biology 401A Biology Essay BEG�M COGAL A species is a genetically distinct group of organisms, which can interbreed and produce fertile, viable offsprings. External similarity is the common basis for identifying individuals as being members of the same species. Yet a bulldog, a terrier, and a golden retriever are very different in appearance, but they are all dogs because they can interbreed. People can also interbreed with one another, and so can cats, but people cannot interbreed with dogs or cats, nor can these with each other. This shows that individuals of a species are able to interbreed with one another but not with members of other species. Even if they could interbreed with members of other species they would not be able to produce fertile offsprings. For example, when horses and donkeys mate, they produce mules. However, these mules are infertile. They are unable to breed at all and bear offsprings of their own. Taxonomy is the branch of biology that deals with the identification and naming of living organisms. The Swedish biologist, Carolus Linnaeus (1707 - 1778) established a simple system for classifying and naming organisms. He developed a hierarchy, or in other words a ranking system for classifying organisms, that is the basis for modern taxonomy. Linnaeu's classification hierarchy included five levels: kingdom, class, order, genus, and species. Modern scientists have added two more classification levels to this, phylum and family. The current classification system divides all organisms into seven major categories, called taxa (singular: taxon). ...read more.

Middle

For many years, bacteria were only classified according to their shape and staining properties. These characters can still be useful in the early stages of identification, but more recent advances in DNA and RNA sequencing can give us a more accurate idea of origins and relationships among these organisms and help us to classify them. The second kingdom is known as kingdom protista. All protists are eukaryotes. They include mostly unicellular eukaryotes but there are also a few samples of multicellular ones. Eukaroyotic cells have nuclei and organelles that are surrounded by membranes. Eukaryotic DNA is contained within a membrane-bound nucleus. The cells of multicellular protists are not specialized to perform specific functions in the organisms. Protists include organisms such as Euglena, Amoebas and Plasmodia. Some hunt for food like animals, and others can make their own food from sunlight using photosynthesis, just like plants. Protists are mainly classified according to the way they move; generally according to whether they use flagella, cilia or pseupodia. For example Euglena uses flagella to move about. It moves about by spinning. The Paramecium has thousands of hair-like cilia, which it beats in a co-ordinated fashion. Last but not least the amoeba moves about through the extension of pseudopdia. However, for the pseudopodia to move an amoeba it must be on a surface of some kind such as submerged rocks. The third kingdom is the kingdom of fungi. Fungi are also eukaryotes. They are mostly multicellular but there are also unicellular fungi such as yeast. ...read more.

Conclusion

Annelids include earthworms; mollusks include clams, oysters, and slugs. They usually have a hard shell. The arthropods are the most highly evolved invertebrates. They include insects, crustaces such as crabs and lobsters and arachnids such as spiders. They have a hard exoskeleton. The invertebrates are classified among themselves according to several criteria such as body symmetry (weather they have radial or bilateral symmetry), presence body segmentation, cephalization (the concentration of important nerves at the end/head of an animal) and type of coelom (type of gut). The vertebrates have a backbone and a nervous system. All vertebrates have a heart and a closed circulation system. Vertebrates include fish, amphibians, reptiles, birds and mammals. Mammals, which include humans, are the most highly evolved forms of animals. Some characteristics, which define mammals, include the presence of fur, sweat glands, and mammary glands. Mammals have an average body temperature of 37 degrees Celsius. Except for exceptions such as the duck billed platypus, which lays eggs, most mammals give birth to their young. Reproduction method is also an import method of classifying animals. Fish have scales. They have no limbs and they move around by swimming. They lay their eggs. Amphibians live in both water and land. They cannot dwell to far from places such as ponds, lakes and so on. They have to lay their eggs in the water. Most reptiles also have scales. They also lay eggs. They do not give birth to their young. Birds have feathers. They have wings and most of them can moves about by flying. They have a body temperature of approximately 42 degrees Celsius. This is because their metabolism needs to work extremely fast in order for them to fly. Birds also lay eggs. ...read more.

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